Telephone system.



No. 856,570. PATENTED JUNE 11, 1907. F. B; 000K & G. NOLEN.

TELEPHONE SYSTEM.

APPLICATION FILED FBJLZ, 1903. RENEWED MAY 17, 1905.

winhl mw UXITEIY) STATES PATENT OFFICE.

FRANK B. COOK AND JAMES G.-NOLEN, OF CHICAGO, ILLINOIS; SAID NOLEN assroNon TO SAID COOK.

TELEPHONE SYSTEM.

N Specification of Letters Patent.

Patented. June 11, 1907.

Application filed February 2, 190a Renewed May 17,1905. SerialNo. 260,857.

. phone Systems, of which the following is a specification.

Our invention relates to telephone systems.

.ingeneral.

- Prior to'our invention, it has been the practice to equip telephone systems with -either annunciators or relays and lamps for enabling the subscribers to signal the opera tor. II annunciators are employed, the sig-- naling currentsentover the line bythe act or the subscriber in calling up central serves "to energize the electro-magnet of the annunciator and thereby cause the'drop or shutter rious ways.

of the annunciator to fall, and thus, give a signal. In a similar manner, a call sent in by a subscriber will energize thelectro-niagnet of a relay, causing it-to attract its armature and thereby close the local circuit ofav signal In either case, however, it .is obvious that the magnetism of-an electro-magnet lamp.

must be depended upon to effect the desired Now electro-magnetic' devices ol this characterthat is to say, annunciators, relays, and like devices-have given more or less trouble and are open to objections in va- For example, devices of this character are'more or less expensive to manuiacture and install, and are not'always re.- liable in use. Relays are allprov'ideil with circuit-closing and opening contacts, and it ,often happens that these contacts become corroded or covered with dust, and thusfail to properly close the circuit when the relay is energized. Again, BlGGtIO-IllfigllfitlU-(l6V1C6S.

of this character'are all capable of offering more or less impedance or retardation tovoice currents, and are also usually of such character as to present considerable resistance to battery current. These and other 1 objections which are well known to those skilled in the art, have tended to render the fuse of annunciators, relays, and the like,

more or less unsatisfactory;

5] lgstated, 18, therefore, the pIOVlSlOIl of a telephone system inv olving suitable call'ln and supervisory signals, such, for examp e, as

a The object of our invention, generally electric lamps, but involving neither annunciators; relays, nor like electro-magnetic switches.

A special object is the provision of a form of automatic switch'which will offer no impedance or retardation to yoice currents, and which will not ofier an undesirable amount of resistance to battery current.-

Another object is to provide a'form of automatic switch which can be cheaply manufaotured and easily installed.

A further object is to. provide a switching device of this character which willbe, absolutely dust proof.

It is also an object to provide certain details and features in a swltcli of-this particular character tending to increase itsgener'al efficiency andserviceability.

Other objects and advantages willfhowever, hereinafter more fully appear.

Broadly considered, our invention contemplates a telephone exchange system without annunciators, relays, or elect'ro-magnetic switches of any kind whatever.

More specifically, our invention contem plates a telephone system equipped with electro-thermal switches for operating the signals. As each switch involves merely a heat-concentrating member and an expansible medium, together with one or more con- *tacts, it follows that a-switch of this character would offer no impedance or retardation to voice currents, and that its resistance to battery current will not in any way be objectionable. Furthermore, as the heat-concentrating member and the expansible n1e ,dium, and also the circuit-closing contacts may be sealed in a glass tube or bulb, it also 'followsthat a switch of this natureis absolutelydust-proof and airtight. 'Again, the construction is so simple that a switch of this character canbe manufactured at a cost far' below that of the ordinary annunciator or relay. I

' In the accom anying draw1ngs, Figure l is a diagram ilustrating a telephone sys-.

As .thusillustrated, the general construc- I tion and circuit arrangement of the system can be of any suitable, known, or approved character. For example, the subscribers apparatus at station A can be suitably cone-t d with the switchboard apparatus 3' board apparatus may also comprise the usual co ircuit consisting of the answering-plug 54 w ll the culling=plhg the two plugs being connected lri aplurality of cord strands. A, calling or linedamp signal Zrof. the usual character can be associated with the'answering jack of the line leading to the substat-ion'A, while a similar lamp signal Ii -can be a sociated with the answering-jack allotted to: the line of substation The supervisory lamps h and l), which are connected in. the

third strand. of the cord-circuit, can be of the usual form or character. With the circuit arrangement shown, a single electroe thermal. switch 1) is associated with the line allotted "to substation A, While a similar.

clectru-t-htrnial switch E is associated with th line leading to substation tire arrangement of the different instruments inv lved in the systenuand also the construct-ion of the dili'erent circuits, will, however,

be more fully understoodby considering the various"operations and circuit connections which take place in v connecting up one subscriber with another.

In I? ig. 1, the subscriber at substation A is supposed to have just lifted his receiver a from the hook-switcl-i (1 therebyolosing the line circuit from the said switch through the coiitacbpoint l, and the. primary 2 of the in-.

duct-ion coil, through the transmitter 3 and the conductor 4, through the main line conductor '5, through the conductor 6'on the switchboard at the central station,throi 1gh the coil or heat-concentrating member 7 of the electro-thermal switch D, through the conductors 8 and 9, through the'nnpedance coil 10 and the conductor 11 to the negative pole of the centralized battery or source'of current 12, through the latter and its positive pole to the conductor 13, through the latter. and impedancecoil 14, thencev through the other coil or heat-concentratingmember 15 of said'electro-thermal switch, through the other limb or conductor 16 of the line leading to the substation A, thence to said hookswitch. The line circuit thus closed causes the current flowing through the coils or heat concentrating members 7 and '15 to generate .sulllc-ient heat to expand the gas in the upper placed into the other leg (F.

This Switchboard apparatus may The. rela-- portion-0f the leg d of the electro-thernial switch, thereby causing the spirits or other conductive medium (1 to be-partialh dislhis displacement of theconductire medium in the electro-therma'l switch operates to close a local circuit from the battery 12, through the conductor l3 and the resistance 17, through the contact-poii'it l8, and the said conductive medium (1, through the other contact-point l9 and the conductor 20, thence through the line lamp 5, through the-conductors 21 and ,9, and thence through the impedance coil 10 and the conductor 11 to the other pole of i said battery. The resistance of thecoi-l 17 is such that the closing of this local circuit- .permits only just enough current to flow through suchcircuit to-light the said lamp. The operator, observing this signal, then in serts the answering plug of. the cord-circuit in'the answering jack allotted to the line of substation A, and then communicates with the calling subscriber in the usual manner. so. as to receive the order for connection.

.W'hen the answering plug is inserted in the jack allotted to the line of substationA, the

connection thus established serves to placethe supervisory lamp b in parallel with the line lamp 1), thus'shunting the latter out.

For, as'explained,'tlie resistance of the coil 17 is such that only su'llicient current to light the line lamp can pass. Thus, in answering the call, the operator automatically -ext1n- 'guishes or restores the line lamp signal.

Upon receiving the order for connection, the operator then inserts the calling plug in one of the multiple jacks allotted to the line of substation C, and then proceeds to call up the subscriber at thisstation in the well known manner. The act of inserting the calling-plug in the multiple jack connected with the line leading to substation C completes a local circuit through the other supervisory lamp 5"- in the following manner: Currentfron'i the positive pole of the battery 12 flows through conductors 22 and 23, through the resistance coils 24 and 25 in parallel, through the conductive medium eof the electro-thermal switch E, through the conductor 26 and the-testing ring 27 of the jack-through the sleeve 2s of the plug, thence through the said lamp I), through the conductors 29 and 30, and thence to the'negativepole of the battery. The resistance of the coil'24 is, like the coil 17, of a charz'icter to permit only sullicicnt current to pass to light the line lamp signal, and is or sullicicntly high resistance to prevent the passage of the subscriber at substation (l. it fo lows that a shunt consisting of the coil 25 and the previous case, connects two cont cts in the 1 electro-thermal switch, and in this case'the This lamp thus caused. to display 'a signal, continues to glow until the-subscriber at.sub-.

station C takes down his receiver, and thus closes the line circuit. at substation C removes hisreceiver 0, thereby allowing the hook-switch c to rise, a line signal is immediately completed from said hook-'switchthrough contact point"31 and the primary 32 of the induction'coil, through the transmitter 33, thence through the limbor line conductor 34 to the central station, through the coil or heat-concentrating member e of the electro-thermal switch E, through the conductor 35 and the impedance coil 36, through the conductor 37 to the negative pole of the battery 12, through the latter to the conductor 22, thence through the impedance coil 38 and the conductor 39, through the -other coil or heat-concentrating member 6 of the said electro-thermal switch, through the ,other limb or line conductor 40, and thence to said hoolcswitch, which completes the circuit. The current flowing through this circuit causes the coils e and e to generate sufficient heat to expand the gas inthe leg 6 of the electro-thermal. swithh sufliciently to cause the shifting conductive medium 6 to become slightly displaced or shifted into the other leg ie. This, as in the contacts 41 and 42, thereby closing the circuit from the saidjbattery through the line lamp e7. But at the same-time it will be seen that .the conductive medium'has shifted out of contact with the other contact 43 'of the electrorthermal switch, thereby opening the shunt extending around .the resistance coil 24. Thus, although a'local circuit has been completed through the line lamp b the latter does'not light up or glow, inasmuch as this lamp is still in parallel with the lamp b", and inasmuch as the resistance of the coil 24 will not permit thepassage of suflicient current to light the two lamps in parallel. In this way, the line lamp allotted to the called subscribers line does not light up or glow when the said subscriber answers the call, but at the same time the automatic restoration or extinguishment of the supervisory lamp b advises the operator that the subscriber has answered the call. The two subscribers are now connected by a complete metallic talking circuit which, of course, includes the tip and ring contacts of thejacks and plugs, and also the tip and ring strands 44 and 45 of the cord circuit. The talking circuit thus estab iislied is, it will be seen, preferably divided into two inductively connected halves or portions by the condensers 46 and 47, which are When the subscriber" interposed in the said tip and ring strands of the cord-circuits.

Now when the subscribers-have finished their conversation and when the receivers at the two substat ons have-been returned to their normal positions on the hook-switches, the line circuits through the coilsor heat-concentrating members of the-two electro-therinal switches are thereby opened and the shifting conductive medium of each electrothermal switch is of course allowed to return by gravity to its normal position. And at. this juncture it is important to note that the battery current has continued to flow through the said coils or heat-concentrating members of the two electro-thermal switches during the conversation between the two subscribers. In other words, closed battery circuits are maintained. through the heatconcentrating members of the two electrothermal switches as long as the subscribers. receivers are,otf the hooks. Butno'w, as stated, the return of these receivers to their respective,hooleswitches opens the line circuits, and permits the coils or hat-concen:

'trating members in the electro-thermal switches to cool off, and thereby allow the. expansive mediuinin said switches to con.- tract and cause the shifting conductive medium to assume its normal condition This action, in'each case, and as previously explained, causes a shunt to .be closed around each of. the two resistance coils 17 and 24, thereby lowering the resistance. of each supervisory lamp. circuit sufficient to permit both lamps to-glow. And, furthermore, the return of the conductive medium to its normal condition in the two electrowthermal switches opens the circuit of each line lamp signal, thus'opening the shunt or parallel connection extending around each supervisory lamp. In other words, when the receiver at substation A is hung up, the'conc;ective medium (1 then returnsto its normal position,

and thereby establishes the normally closed shunt connection around the resistance coil.

17, which shunt connection comprises the resistance coil 48 and the said conductive medium (1. The resistance of the coil 17 thus being materially shunted, sufficient current then flows through the local circuit including these two coils l7 and 48 to cause the lamp 7) to glow. And in a similar manner, the hanging uof the receiver at substation C closes the s iunt connection consisting of ,the coil 25 and the conductive medium thereby so materially shunting the resistance of the coil 24 that sutlieient current then flows through the local circuit to cause the lamp 7)" to glow. 'lhus one electro-thermal switch is allotted to each line. and these electro-thermal switches not only control the line signals, but also control the supervisory signals. That is to say. one electro-theruial switch is allotted to each line, and each switch is under the control of the subscriber for the purpose of first causing the line signal to glow, and then, after the call has been answered and the pluginserted, for causing the supervisory lamp in the cord-circuit to glow for the purpose of giving the opera tor a signal for disconnection.

The construction of the electro-thermzil switches can be varied considerably without departing from the spirit of our invention.

Fig. 2 illustrates the construction of the electro-tlieri'nalswitch E, shown in Fig. 1. The conductive medium- 6 c2 i be-of any suitable character, as, for example, it may 0011- sist of a suflicient quantity of spirits. Again, it mayconsist of mercury or mercury and'spi'r its. It is preferable, howevento seal the saidconductive medium and the coils or heat-con .centrating members e, e up 'in a vacuum, so as to prevent oxidation of any of the elements thus inclosed in the glass tube or bulb; and under such conditions the conductive medium e is preferably of a character to evapoof the conductive medium; Nithan automatic switch 'of this character, the coils or heat-concentrating members can, if desired, be placed in any of the circuits through which it is necessary for voice currents to travel, and under such conditions the coils or heatconcentrating members offer no impedancev or retardation, such. as is characteristic of a relay or annunciator. switching device of this character is peculiarly. adapted to a'ciitcuit arrangement which necessitates a constant ,flow of battery current' through the switch during the time the subscribers are talking, such, for example, as the circuit arrangement shown in Fig. 1i 'That is to say, in-v a circuit arrangement such as shown in Fig.1, a flow of battery current is necessarily maintained. through the automatic line switches id uring the conversation between the two subscribers, inasmuch as it is the restoration'of these swit'chesto their normal conditions which operates to cause a display ofthe supervisory signals. To thus maintain a flow of battery current through an ordinary line relay during a long conversation would result in an injurious and undes sirable heating of the relay. But inasmuch as our improved line 'switchis dependent upon the generation of heat forits operation, and is thus inherently thermal in c araoter, it follows that a constant flow of battery current can have no' injurious efiect, and that the subscribers can carry on their conversa tion for any length oftime without in anywav injuring the automatic line-switches, which remain o erated duringsuch conver- 6 sation. With t e arrangement ,illustrated,

And, furthermore, .a

' parallel.

responded. cuit' will obviously only include the, superwhat little resistance the heat-concentrating neinbers offer to the flow of battery current is equally balanced-one member being located in one side of the line circuit, and the other member being located in the other side of said circuit.

Inclosed, as they are, within a hermetically sealed glass tube or bulb, the

construction of electro-thernial switch.

- As far as the broader purposes of our invention is concerned, the test which the operator 1 su allyinakes for the purpose of as certaini-ng whet-her a l'ine'is busy, before a connection 'is' made with such line, can be made in the tSt-ftl way-by totiching the tip of 'the calling plug to the test ring of the jack connectedqwith the called 'subscribers line. For example, as shown in Fig. 1, the test circrit, when the called subscribers receiver is] ofithe hook and when no plugs are in any f the jacks'connected with his line, will extend from the negative pole of the battery and will include the line lamp, the contacts 42 and 41, the testing ring of the ja clg-the tip contact and tip strand of the cord-circuit,

and one coil of the operators head telephone -X in the cord-circuit of the operator making the test and'back to the other pole of the battery 12. Now, on the other hand, should 'it happen that the called subscribers line is busy,that is to say, that his receiver is off the hookand the'phzg of one-0f the cord-cir- 0" its is in a jack connected with his line, then, in such case, the test circuit completed by the act of another operator touching the tip of her calling phg to the jack connected withhis line, will not only include the supervisory lar'np, but alsothe line lamp, it being observed t-hat' thetwo are then'connected in Th s in either case, the test' circuit includes the line lamp, either alone or in parallel'with the supervisory-lamp, and 'in either case a local circi it is completed from one pole of the battery to the. other which includes the operators head telephone, and in either case, the constant flow of current through this closed local circuit will serve in the usual and well known manner to advise the operator that the line. is. already in use. It will be understood that the test circuit in either case, but particularly when a subscriber has simply taken down his receiver andhas not received an answer from central,

' includes the liquid condrctive medium of the electro-thernial switch. Suppose, however, that the "called subscriber has already been called by another operator but has not yet Now, in such case, the test cirvisory lamp in the cord-circuit of the operator making the test. These test circuits 1 ranged, these no plugs in any of the jacks,

conductors, and are consequently are obviously and not capable 0t ofi'er ng impedance or re 'tardation to voice currents in the manner cuits be modilied or changed to any extent without departing troin the spirit of our iiiinvent-ion is concerned. if the line is bisy,

in anyol the three ways indicated, a click will be produced in the operators head telephone, indicating that the hue is either in use or being held for use. But it there are scribers telephone is on the hook, then there will be no click in the operators telephone. But this method of testing is well understood by those skilled in the art and need not-be further described.

The fact that our improved electro-thernial switch or circuit-closing and breaking device is non-inductive in character is of great importance, especially in connection with circuits where it is found desirable to locate the coils or heat-cgncentrating members directly in the talking circuit. For example, in Fig. 3 the two coils of the electrotherinal switch constitute a part of the line connection between the jacks and the line directly in the talking circuit. But even when thus arcoils or l1eat-concentrating members can offer no retardation or impedance to voice currents, inasmuch as they non-inductive in character,

* which is necessarily characteristic of a relay,

' r ed,

annunciator, or other similar device involving a helix and soft iron core. Thus, as (Si-- our invention contemplates an automatic switch which is non-magnetic and non-inductive in character, and which may, therefore, be located in any of the conductors of a telephone system, regardless oi? whether or not these conductors are i talking purposes.

employed for I claim as my invention of a subscribers line, a line lamp signal, a centrallz'ed'source of current connected. with 'the line, a subscribers hook-switch for open.

ing and closing the line; circuit, a normally open circuit includingsaid lamp signal and source of current, and a non-inductive switch circuit also including the normally open contacts of said, non-inductive switch.

2. In a telephone system, the combination of a subscriber's line c1rcu1t,,mcans for supplyingcurrent to said circuit, a line lamp signal associated with the line at the central station,

1-. In a telephone system, the combination .vention, as far as the broader aspect of the and if the s -bl a normally open local circiut including said lamp and source of current, and a non-in ive circuit-closing device adapted to be operated by current flowing through saidline same at the central station,

circuit and adapted for closing said local circuit.

3. In a telephone system, the combination. of a subscribers line circuit, a centralized battery for supplyinglcurre ntto said line circuit, means at the subscribers station for opening and closing the line circuit, artelectro-thermal switch associated with the line at thecentral station and adapted to be controlled by the subscriber, and a line signal connected and arranged to be controlled by said switch.

4. In a telephone system, the combination of a subscribers line circuit, means under the control of the subscriber for causing a llow of current in said line circuit, a visual. signal associated with the line at the central station,

and a thcrmal'device for controlling the display of said signal, said device being in turn under the control of the subscriber.

control of the subscriber for supplying current to said circuit, line and supervisory signals located at the central station, and a single non-inductive and non-magnetic electrothernial circuit-closing-dcvice connected and arranged for controlling both of said signals, and adapted to be controlled by means located at the subscriber's station.

6. A telephone system comprising substations equipped with suitable substation apparatus, a central station'equipped with suit able switchboard apparatus, suitable line connection between the switchboard apparatus and the substations, said switchboard apparatus including line and supervisory visual signals, and also including -a plurality of electro-thermal switches, one for each line, adapted to be controlled by means located at the substations, and adapted in turn to control the display of said signals.

- 7. In a telephone system, and in combination with subscribers telephones and opera cords and with a for operating the a circuit-closing device for said signal consisting ot a hermetically sealed receptacle, and ol" a suitable heat concentrating member and expansive medium, together with suitable contacts and a conducting medium inclosed within said receptacle.

8. In a telephone system, and in combination with subscribers telephone and operators plugs and connecting cords and with a visual signal and a battery for operating the same at the central station, a circuit-closing device consisting of a hermetically sealedreceptacle, and of a heat-coil and expansive medium, together with suitable contacts and a conducting medium, included within said receptacle.

9. in a telephone system, the combination 'of a subscribers line circuit, a line lamp sigtors plugs and connecting visual signal and a battery signaling device arranged to be operated by the said switch, a plug-cordconnecting circuit tor the line, a supervisory signaling device associated with the plug-cord circuit,

and circuit connections whereby one said signaling device nection is nludcWltll the in use.

21. A telephone line, an electro-thermal line and the line is switch associated therewith, a line lamp associated with the line and connected in circuit with a source of electricity and normally open contacts of the switch, comwcting ,means for the line, a supervisory lampasso- I5 ciated with the connecting means, the said switch being adapted and arranged to close the circuit of the said source through the line lamp when the line circuit is closed, and circuit connectionswhereby the supervisory" lamp shuntsthe hue lamp out and the line lamp rhunts the supervisory lamp to keep it from displaying a signal, when connection is made with the line and the line is in use.

22. In a telephone system, a

spring jacks at a central station, an electrothermal switch and a source of electricity bridged across the said line at the central station, a manually-operable switch at the sub- 3 scribers station, a line signaling device in circuit with a source of electricity and nor mally open contacts of the electro-thermal switch, a plug-cord connecting circuit for the line, a supervisory signaling device associated with the plug-cord circuit, the closing of the switch at the subscribers station causing the electro-thermal switch to close the said normally open contacts and thereby cause the line signaling device to display a signal, and

4 suitable circuit connections whereby the su-- pervisory signaling device shunts the linesignaling device and renders same inactive, and whereby theline signaling device shunts the supervisory signaling device and renders same inactive, substantially as described.

In a telephone system, a metallic line extending from a subscribers station to suit. able spring jacks at a central station, a transmitter, receiver, bell, and normally open 5 switch at the subscribersstation, an elcctrothermal switch and a source ol electricity bridged across the limbs of the line at the central station, a line lamp' in circuit with the said source of electricity and normally open con tacts of the electro-thermal switch, a metallic plug-cordcircuit for the line, terminating in suitable connecting plugs adapted to cooperate with the s Jring jacks, a test ring for each jack and'ali connected together and I through a suitable resistance to the source of electricity, a third strand for each connecting cord, terminating in a third contact of its connecting plug and adapted to be connected with the test ring of a spring jack when con- 5 nection is made with the line, a supervisory shunts the other out when con,

circuit, of an line extendt l v I 5 ing i'rom asubscribers station to suitable 1n the. sald chamber,

coils. in circuit lamp in circuit witha said third strand and the source of electricity, and a suitable operators circuit and busy-test arrangement for the plug-cord circuit, the closing ofthe normally open switch at the subscribers station closing the circuit of the said source through the electrothermal switch and thereby heating same and closing the said normally open contacts therein to light 'the line lamp, the connecting plug, when connected with a spring jack Oflllt line, placing the line lamp and supervisory the supervisory lamp shunts the line lamp out and the line lamp shunts the supervisory lamp out, the opening o'f'the switch at the subscribers station restoring the electro thermal switch to its normal condition and opening the circuit of the line lamp shunt about the supervisory lamp to allow the latter to glow. i

24. The combination with a telephonedine electro-thermally-operablc device associated therewith and comprising a sealed chamber, heat-producing means witha gas within the said chamber arranged to be expanded by heat from the heat-producing means, a conducting liqluid in the said chamber arranged to be movec the said gas, suitable circuit terminals within by the expansion and contraction of lamp in multiple whereby the said chamber arranged to be connected or. J

disconnected by the conducting nals; a line signaling device arranged to be operated by the said electro-thermally-oper a le dev ce when the latter is heated by ourrent'over the line, and means for shunting the line signal out when connection is made with the line. v

25. In a telephone system, the combination of a metallic line extending from a substation to the central station, a switch at the substation for closing and opening the circuit of the metallic line, an electro-thermallyo erable device associated with the line at t 1e central station and comprising a sealed chamber, heat producing coils in circuit with the respective limbs of the metallic line and within the sealed chamber, a gas within the said chamber s'uitably'disposed'to be ex pandcd by heat rem the heat-producing coils, a conducting liquid in the said chamber suitably disposed to be shifted by the expansion and contraction of the said gas, suitable circuit terminals within the said chamber arranged to be connected or disconnected by the conducting liquid, and suitable circuit connections to the said terminals; impedance with the respective heatpro ducing coils, a source of electricity in circuit with the said impedance coils, the heat-prcducing coils, and the limbs of the metallic line, suitableconnection terminals connected in multi' is to the linibs of the line, a test ring for eac connection terminal all connectliquid, and-- suitable circuit connections to the said termireg I the switch at the substationcausingthe said device to close the last mentioned disconnecicil terminals and light the line lamp, asecond Y resistance normally connected in multiple Withthe other said resistance, and

cut out of circuitwith the said test rings by:

the said device when thelatter is heated, a metallic plug-cord connecting circuit for the line, a third strand of a cord and plug, containing a supervisory signal lamp connected" in circuit wlth the said source and arranged to, be ccmiected with the said test rings when connection is made with the line, the super- Withthe line lamp and shunting the latter out, the line lamp alsoshunting the supervisorylamp to render it inert, and the electro-thermal'ly-operable device opening the circuit of the linelan'ip and again placing the 1 twoj said resistances in multiple in the supervisory lamp circuit to light the supervisory lamp, when the switch at the substation is again opened. H Signed by us at ChicagofCook county Illinois, this 17th day of an'uar'y, 11903.

* FRANK BQcocK.

v I I AMES G. NOLEN.

Witnessesi WM. A. HARDERS, p HARRY P. BnUMGARTNER.

visory lamp now being connected in multiple I 

